Bug: in resolving extras for `requirement`

[pavel-hiiro]

Hi! Thanks for a great library!

I believe there is a misspell in a checking parsing extras paths for requirements

	# Requirements
	if using == "requirements":
		requirementsPaths = ["requirements.txt"] if len(extras) > 0 else extras
		extras = []

which should be simply fixed by changing line to

		requirementsPaths = extras if extras else ["requirements.txt"]

which is consistent with the previous logic
ba70665#diff-3d2b023624ae6455c661f617085c9570286f1bed0e80cb02a65512d802aa19b4L58-L60

[FredHappyface]

Hi sorry for the delay in getting back to you! Life has been busy

You're absolutely spot on, can't believe I introduced a bug there. I'll fix this asap